This is a NIDA Cutting-Edge Basic Research Awards (CEBRA) proposal in the R21 format. We have made progress towards developing a set of modified K+ channel subunits used as molecular tools for manipulating neuronal electrical excitability in vivo in specific neural circuits in Drosophila. From our preliminary results, we can effectively alter specific behaviors and cellspecific signal transduction events by expressing modified K+ channel genes. This transgenic manipulation appears to exert no ill effects on neuronal survival in vivo (Nitabach et al., 2002a; Nitabach et al., manuscript in preparation). This successful implementation in Drosophila provides strong motivation to translate this new technology to specific neural circuits in transgenic mice. My Specific Aims are: (1) Express modified potassium channel genes in vitro in dissociated mammalian neurons and test for the robustness of channel gene expression, the effectiveness of neuronal electrical silencing, and neuronal viability. Candidate genes that meet these criteria will be used for the subsequent Aim. (2) Construct and characterize transgenic mice that express modified potassium channel genes targeted by the highly specific neuronal promoter L7. Characterization will consist of electrophysiological and imaging analysis. Successful translation of this technology to transgenic mice will provide a powerful gene-targeted based method to complement widely-used existing pharmacologic and lesion strategies for studying neural circuits that are linked to addiction and drug abuse.